CodeWars - SquareEveryDigit

public static int SquareDigits(int n)
    {
        string input = n.ToString().TrimStart('0');
        StringBuilder output = new StringBuilder();

        int length = input.Length;
        for (int i = 0; i < length; i++)
        {
            int squareNum = int.Parse(input[i].ToString());
            int result = squareNum * squareNum;
            output.Append(result.ToString());
        }
        int number = int.Parse(output.ToString());
        return number;
    }
}